Description
Direct Mill Supply, Zero Broker Markup — Raw Q235B and Q345B square and rectangular hollow sections produced and fabricated under one roof, eliminating third-party material sourcing gaps.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B/Q345B Carbon Steel Square/Rectangular Pipe |
| Product Type | Square / Rectangular Steel Tube (Hollow Section) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, SS400, Q460, SS330, SS540 |
| Standard | ASTM |
| Section Shape | Square / Rectangular / Round |
| Size Range | Wall Thickness 0.5–200 mm |
| Length | 12 m (or customized) |
| Technique | Cold Rolled / Hot Rolled |
| Surface Treatment | Galvanized / Oiled / Bare (per consumer requirement) |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Fluid Pipe / Boiler Pipe / Drill Pipe / Hydraulic Pipe / Gas Pipe / Steel Structures / Construction Frames / Machinery |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC & General Contractors | Structural steel frames for industrial warehouses, logistics centers, and commercial buildings |
| Industrial Plant Builders | Equipment support structures, conveyor frames, and platform columns |
| Pipeline & Utility Contractors | Hydraulic and gas transport pipelines for low-pressure distribution systems |
| Machinery Manufacturers | Load-bearing frames, crane booms, and base structures for heavy equipment |
| Infrastructure Developers | Bridge railings, sound barrier supports, and foundation pile casings |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on Q345B rectangular tubes prevents cumulative dimensional drift across multi-story connections.
When procurement teams source ASTM Carbon Steel Square Rectangular Hollow Section Supplier materials from trading companies rather than integrated mills, wall thickness variance compounds at every beam-to-column junction. I have seen entire warehouse frames rejected during third-party inspection because negative tolerance exceeded 0.3 mm on critical load-bearing members — the rework cost tripled the original material savings. Without mill-level control over rolling schedules and real-time thickness monitoring, buyers inherit dimensional uncertainty that no amount of post-fabrication machining can fix. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
Matching Hollow Section Profiles to Structural Load Paths
Q235B and Q345B grades cover the majority of non-pressure structural applications where yield strength requirements fall below 345 MPa. For warehouse frames and industrial platforms, rectangular sections provide flat bearing surfaces for bolted or welded connections, while square tubes offer uniform torsional resistance for column applications. The ±1% wall thickness tolerance ensures that connection plates fit flush without shimming — a detail that saves hours of field adjustment on projects with hundreds of nodes. Our CNC cutting and drilling lines process these ASTM Carbon Steel Square Rectangular Hollow Section Supplier products directly to engineered shop drawings, eliminating the coordination gap between material supply and fabrication.
Engineering Compliance Across International Standards
Structural hollow sections for EU projects must conform to EN 10219 (cold-formed) or EN 10210 (hot-formed) with CE marking, while North American specifications typically reference ASTM A500 or A1085. The Q345B grade roughly corresponds to S355JR in the EN system and ASTM A579 Grade 50 in US standards — but equivalence is not automatic. Mill test certificates must document chemical composition and mechanical properties against the specified standard, and third-party inspectors (SGS, BV, TüV) verify traceability from heat number to finished section. For projects requiring EN 1090 execution class 2 or higher, the fabricator’s welding procedures (WPS/PQR) and welder qualifications must be certified — documentation gaps here delay customs clearance and site installation. [NEED_CITE: steel grade equivalence between Chinese GB, European EN, and American ASTM standards]
Understanding Grade Selection and Manufacturing Process
The Q-series (Q195, Q235, Q235B, Q345, Q345B, Q460) follows the Chinese GB/T 700 and GB/T 1591 standards, where the number after “Q” indicates minimum yield strength in MPa. Q235B is the workhorse grade for general construction — adequate for warehouse frames, stairways, and non-critical machinery supports. Q345B offers higher strength for longer spans or heavier loads, reducing section weight while maintaining structural integrity. For Japanese-specification projects, SS400, SS330, and SS540 align with JIS G3101 rolled steel requirements.
Hot-rolled hollow sections (produced from plate or coil) suit thicker walls above 6 mm and applications requiring superior corner mechanical properties. Cold-rolled (cold-formed) sections achieve tighter dimensional tolerances and smoother surfaces for visible architectural applications. Surface treatment selection depends on the service environment: galvanized coating provides sacrificial protection for outdoor or high-humidity installations; oiled surfaces prevent transit corrosion for indoor or painted end-use; bare (black) sections are specified when field welding or custom coating will occur after delivery.
Hidden Costs of Sourcing from Unverified Suppliers
Ordering ASTM Carbon Steel Square Rectangular Hollow Section Supplier products without verified mill test certificates creates cascading risks: material arriving at site may fail ultrasonic testing, forcing replacement orders that delay project completion by weeks. Negative tolerance beyond specification limits reduces load-bearing capacity — a 10% wall thinning on a critical column can drop its buckling resistance below design requirements. Certification mismatches (e.g., receiving GB-standard material on an EN-specified project) trigger customs holds and re-inspection costs that erase any initial price advantage. [NEED_CITE: consequences of material non-compliance in international steel procurement]
Why Integrated Mill and Fabrication Changes the Procurement Equation
Our facility operates three production lines for raw steel and maintains over 2,800 hollow section specifications in inventory — this vertical integration means the Q345B rectangular tubes we fabricate into trusses come from the same heat as the material we sell as finished sections. Every batch carries full traceability from iron ore to final dimension, documented in mill test certificates that satisfy EN 10204 3.1/3.2 requirements. We hold CE certification for EN 10219 and EN 10210, ISO 9001 quality management, and accept third-party inspection from SGS, BV, and TüV at any production stage. Our engineering team reviews shop drawings for material optimization before fabrication begins — a service that typically reduces steel tonnage by 5-8% through section size rationalization. Professional loading plans maximize container utilization for 12 m lengths, and we coordinate door-to-door logistics with complete export documentation.
Documentation & Compliance
- Mill test certificate documenting Q235B/Q345B chemical composition (C, Mn, Si, P, S) and mechanical properties (yield strength, tensile strength, elongation) per GB/T 700 and GB/T 1591
- CE certificate confirming EN 10219 cold-formed or EN 10210 hot-formed hollow section compliance for EU market access
- ISO 9001 quality management system certificate covering steel production, fabrication, and inspection processes
- SGS or BV third-party inspection report verifying dimensional accuracy, surface treatment thickness, and welding quality per project specifications
- Material traceability documentation linking each bundle to heat number, production date, and test results
- Complete customs documentation package including packing list, bill of lading, and certificate of origin for destination-country clearance
Packaging, Loading & Delivery
- Q235B and Q345B square and rectangular tubes bundled with galvanized steel strips at 1.5 m intervals, with edge protectors preventing zinc coating damage during transit
- Galvanized hollow sections wrapped in waterproof plastic sheeting to preserve surface finish during ocean freight; oiled sections sealed to prevent contamination
- 12 m standard lengths loaded in 20ft and 40ft containers using optimized stowage plans — a 40ft high-cube accommodates approximately 22-25 tons of rectangular tubes depending on wall thickness
- Custom cut lengths (6 m, 9 m, or project-specific) available with CNC saw cutting, bundled separately with length markings for site identification
- Each bundle tagged with heat number, steel grade (Q235B/Q345B), section dimensions, and wall thickness for immediate site verification
- FOB, CIF, and DDP shipping terms available; door-to-door delivery coordinated with freight forwarders experienced in oversized steel cargo
Starting Your Procurement Process
Share your project drawings (PDF or DWG format), steel grade requirements, section dimensions, and quantity with our engineering team. We respond within 24 hours with a preliminary technical assessment, detailed quotation including material and fabrication costs, and a shop drawing timeline. For ASTM Carbon Steel Square Rectangular Hollow Section Supplier inquiries requiring EN 10219 or ASTM A500 compliance, specify the standard and execution class in your initial request so we can confirm certification coverage and third-party inspection availability.
Frequently Asked Questions
Q: What is the difference between Q235B and Q345B for structural applications?
A: Q235B offers minimum 235 MPa yield strength and suits general construction frames, stairways, and non-critical supports. Q345B provides 345 MPa yield strength for longer spans, heavier loads, or weight-optimized designs. Both grades are available in square and rectangular sections with full mill test certification.
Q: Can you fabricate hollow sections to custom drawings with cutting, drilling, and welding?
A: Yes. Our fabrication division processes ASTM Carbon Steel Square Rectangular Hollow Section Supplier products through CNC cutting, plasma cutting, drilling, bending, and welded assemblies per your shop drawings. We provide welding procedure specifications (WPS) and welder qualifications certified to AWS and EN standards.
Q: What is the minimum order quantity for custom sizes or small projects?
A: The MOQ is 5 tons for standard stock sizes. For non-standard dimensions or custom fabrication, we evaluate case-by-case based on section complexity and production scheduling.
Q: Which surface treatment should I specify for outdoor structural applications?
A: Hot-dip galvanized coating provides long-term corrosion protection for outdoor exposure — typical coating thickness ranges from 45-85 microns depending on service environment. For indoor or painted applications, oiled or bare (black) surfaces are more economical. We can advise based on your project’s environmental conditions and design life.
Q: What quality documentation do you provide for EU or international projects?
A: We supply EN 10204 3.1/3.2 mill test certificates, CE marking for EN 10219/EN 10210 compliance, ISO 9001 certificates, and accept third-party inspection from SGS, BV, or TüV. Complete documentation packages include welding records, dimensional inspection reports, and coating thickness measurements.
Get Your Technical Assessment and Quotation
Submit your project specifications, steel grade requirements, and target delivery date to receive a detailed quotation with mill test certificate samples and fabrication timeline within 24 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjystructure.com
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
